Following our review of Instances of system frequency outside the normal operating band we analyse data from the “mandatory PFR era” to understand whether the number of days per month is changing under current conditions.
We count the number of days each month when there was at least one 4-second measurement outside the NOFB.
The chart below shows:
- Below NOFB events are more frequent than above NOFB events.
- A trend for days increasing or decreasing is not apparent.
Table of contributing days
Each contributing day in the monthly chart is itemised in the following table. Where possible, time permitting, we’ve linked to previous WattClarity articles that discuss events on the day (which may or may not be directly related to system frequency).
| Month | Days (Date, frequency direction) |
| 2025-08-01 | Tue 19 Above NOFB Fri 29 Below NOFB |
| 2025-06-01 | Mon 16 Below NOFB |
| 2025-05-01 | Mon 26 Below NOFB |
| 2025-04-01 | Fri 11 Above NOFB Sat 19 Below NOFB |
| 2025-03-01 | Wed 05 Below NOFB Mon 31 Below NOFB |
| 2025-02-01 | Thu 13 Below NOFB |
| 2025-01-01 | Sun 12 Below NOFB Wed 15 Below NOFB Mon 27 Below NOFB |
| 2024-12-01 | Tue 03 Below NOFB Sun 08 Above NOFB |
| 2024-11-01 | Wed 06 Below NOFB Tue 12 Below NOFB Wed 13 Below NOFB Fri 22 Below NOFB |
| 2024-08-01 | Sun 11 Below NOFB Wed 14 Below NOFB Mon 19 Below NOFB Fri 23 Below NOFB |
| 2024-07-01 | Wed 10 Below NOFB |
| 2024-04-01 | Wed 03 Below NOFB |
| 2024-03-01 | Thu 21 Below NOFB Fri 29 Below NOFB |
| 2024-02-01 | Thu 08 Below NOFB Tue 13 Below NOFB Mon 19 Above NOFB Fri 23 Below NOFB |
| 2024-01-01 | Mon 08 Below NOFB Thu 18 Below NOFB |
| 2023-12-01 | Mon 04 Below NOFB Mon 11 Below NOFB Sun 17 Below NOFB Sun 31 Below NOFB |
| 2023-11-01 | Thu 09 Above NOFB |
| 2023-09-01 | Tue 26 Below NOFB Sat 30 Below NOFB |
| 2023-08-01 | Thu 17 Below NOFB Sun 20 Below NOFB |
| 2023-07-01 | Wed 05 Below NOFB |
| 2023-06-01 | Mon 12 Below NOFB |
| 2023-05-01 | Sun 07 Below NOFB |
| 2023-03-01 | Sat 18 Below NOFB Thu 23 Below NOFB Thu 30 Below NOFB |
| 2023-02-01 | Tue 07 Below NOFB |
| 2023-01-01 | Sat 14 Below NOFB Thu 26 Below NOFB Sun 29 Below NOFB |
| 2022-12-01 | Mon 05 Below NOFB Tue 06 Below NOFB Mon 12 Below NOFB |
| 2022-11-01 | Tue 01 Below NOFB Fri 11 Below NOFB Wed 16 Below NOFB Sun 20 Below NOFB |
| 2022-10-01 | Thu 13 Below NOFB |
| 2022-09-01 | Sat 03 Below NOFB |
| 2022-08-01 | Thu 11 Below NOFB |
| 2022-07-01 | Tue 05 Below NOFB |
| 2022-06-01 | Fri 03 Below NOFB Wed 15 Below NOFB Thu 16 Below NOFB Fri 17 Below NOFB Sat 18 Below NOFB Fri 24 Below NOFB |
| 2022-05-01 | Thu 12 Below NOFB Tue 31 Below NOFB |
| 2022-04-01 | Wed 06 Below NOFB Thu 07 Below NOFB Sat 23 Below NOFB Mon 25 Below NOFB |
| 2022-02-01 | Tue 08 Below NOFB Sat 19 Below NOFB Mon 21 Below NOFB |
| 2022-01-01 | Fri 07 Below NOFB Sat 29 Below NOFB |
| 2021-12-01 | Wed 01 Below NOFB Mon 13 Below NOFB Fri 31 Below NOFB |
| 2021-08-01 | Tue 10 Below NOFB Sat 21 Below NOFB Wed 25 Below NOFB |
| 2021-07-01 | Sat 24 Below NOFB |
| 2021-06-01 | Tue 01 Below NOFB |
| 2021-05-01 | Fri 07 Below NOFB Mon 10 Below NOFB Fri 21 Below NOFB Tue 25 Below NOFB |
| 2021-04-01 | Mon 05 Below NOFB Thu 29 Below NOFB |
| 2021-03-01 | Wed 10 Below NOFB Sat 20 Above NOFB Fri 26 Below NOFB Wed 31 Below NOFB |
| 2021-02-01 | Tue 02 Below NOFB Mon 22 Above NOFB Sun 28 Below NOFB |
| 2021-01-01 | Sat 02 Below NOFB Wed 13 Below NOFB Sun 17 Below NOFB Sun 24 Above NOFB |
Frequency within the NOFB?
In 2024 we analysed distributions of frequency in NEM Mainland frequency patterns – historical overview from 2024.
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